Sally Field, who won an Oscar for portraying a textile union activist in the movie Norma Rae , has become the first major star to endorse the dissident slate challenging the current leadership of the Screen Actors Guild. In a statement on Thursday, Field urged guild members to vote for the Unite for Strength slate in September's board elections to "end the senseless war with AFTRA and start building a united front of actors." The union's national board is set to meet on Saturday. Although some reports had suggested that the board might agree to submit the studios' "final offer" to the membership for a vote, Daily Variety said today that such action was "unlikely."